Evolution has produced enormous variety in insects. Pictured are some possible shapes of antennae.
Diagram of biramous leg of a trilobite; Agnostus spp.
A pie chart of described eukaryote species, showing just over half of these to be insects
Crustacean appendages
Insects with population trends documented by the International Union for Conservation of Nature, for orders Collembola, Hymenoptera, Lepidoptera, Odonata, and Orthoptera. Of 203 insect species that had such documented population trends in 2013, 33% were in decline.
Micrograph of housefly leg
Stylized diagram of insect digestive tract showing malpighian tubule, from an insect of the order Orthoptera
Diagram of a spider leg and pedipalp – the pedipalp has one fewer segment
Bumblebee defecating. Note the contraction of the abdomen to provide internal pressure
The leg of a squat lobster, showing the segments; the ischium and merus are fused in many decapods
The tube-like heart (green) of the mosquito Anopheles gambiae extends horizontally across the body, interlinked with the diamond-shaped wing muscles (also green) and surrounded by pericardial cells (red). Blue depicts cell nuclei.
Seven-segmented legs of Scutigera coleoptrata
The different forms of the male (top) and female (bottom) tussock moth Orgyia recens is an example of sexual dimorphism in insects.
Zabalius aridus showing full leg anatomy, including plantulae under each tarsomere
Gulf fritillary life cycle, an example of holometabolism.
Diagram of a typical insect leg
Most insects have compound eyes and two antennae.
Acanthacris ruficornis, legs saltatorial, femora with bipennate muscle attachments, spines on tibiae painfully effective in a defensive kick
A cathedral mound created by termites (Isoptera).
Robber fly (Asilidae), showing tarsomeres and pretarsi with ungues, pulvilli and empodia
White-lined sphinx moth feeding in flight
Webspinner, Embia major, front leg showing enlarged tarsomere, which contains the silk-spinning organs
The backswimmer Notonecta glauca underwater, showing its paddle-like hindleg adaptation
Bruchine with powerful femora used for escape from hard-shelled seed
Perhaps one of the most well-known examples of mimicry, the viceroy butterfly (top) appears very similar to the monarch butterfly (bottom).
Expression of Hox genes in the body segments of different groups of arthropod, as traced by evolutionary developmental biology. The Hox genes 7, 8, and 9 correspond in these groups but are shifted (by heterochrony) by up to three segments. Segments with maxillopeds have Hox gene 7. Fossil trilobites probably had three body regions, each with a unique combination of Hox genes.
European honey bee carrying pollen in a pollen basket back to the hive
Aedes aegypti, a parasite, is the vector of dengue fever and yellow fever
Because they help flowering plants to cross-pollinate, some insects are critical to agriculture. This European honey bee is gathering nectar while pollen collects on its body.
A robberfly with its prey, a hoverfly. Insectivorous relationships such as these help control insect populations.
The common fruit fly Drosophila melanogaster is one of the most widely used organisms in biological research.

Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed legs, compound eyes and one pair of antennae.

- Insect

The legs of insects and myriapods are uniramous.

- Arthropod leg
Evolution has produced enormous variety in insects. Pictured are some possible shapes of antennae.

11 related topics



Crustaceans (Crustacea ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp.

Crustaceans (Crustacea ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp.

A shed carapace of a lady crab, part of the hard exoskeleton
Body structure of a typical crustacean – krill
Abludomelita obtusata, an amphipod
Eggs of Potamon fluviatile, a freshwater crab
Zoea larva of the European lobster, Homarus gammarus
Copepods, from Ernst Haeckel's 1904 work Kunstformen der Natur
Decapods, from Ernst Haeckel's 1904 work Kunstformen der Natur
Eryma mandelslohi, a fossil decapod from the Jurassic of Bissingen an der Teck, Germany
Norway lobsters on sale at a Spanish market

Some crustaceans (Remipedia, Cephalocarida, Branchiopoda) are more closely related to insects and the other hexapods than they are to certain other crustaceans.

They are distinguished from other groups of arthropods, such as insects, myriapods and chelicerates, by the possession of biramous (two-parted) limbs, and by their larval forms, such as the nauplius stage of branchiopods and copepods.


Arthropods (, (gen.

Arthropods (, (gen.

Structure of a biramous appendage.
Alignment of anterior body segments and appendages across various arthropod taxa, based on the observations until mid 2010s. Head regions in black.
Illustration of an idealized arthropod exoskeleton.
Cicada climbing out of its exoskeleton while attached to tree
Arthropod eyes
Head of a wasp with three ocelli (center), and compound eyes at the left and right
Compsobuthus werneri female with young (white)
The nauplius larva of a penaeid shrimp
Marrella, one of the puzzling arthropods from the Burgess Shale
The velvet worm (Onychophora) is closely related to arthropods
Insects and scorpions on sale in a food stall in Bangkok, Thailand

One arthropod sub-group, insects, is the most species-rich member of all ecological guilds in land and freshwater environments.

These would later fuse into a single pair of biramous appendages united by a basal segment (protopod or basipod), with the upper branch acting as a gill while the lower branch was used for locomotion.


Arthropod group which also includes millipedes and other multi-legged creatures.

Arthropod group which also includes millipedes and other multi-legged creatures.

Underside of Scolopendra cingulata, showing the forcipules
Close-up of the tail-like rear pair of legs of a centipede
A representative millipede and centipede (not necessarily to scale)
A centipede protecting her first instar offspring
A centipede (Scolopendra cingulata) being eaten by a European roller
A juvenile centipede seen on vegetation at Agumbe, Karnataka, India
Centipedes at Wangfujing market
Man holding Scolopendra gigantea. Trinidad, 1961

Within these habitats, centipedes require a moist microhabitat because they lack the waxy cuticle of insects and arachnids, therefore causing them to rapidly lose water.

The forcipules are modifications of the first pair of legs (the maxillipeds), forming a pincer-like appendage always found just behind the head.


Coleoptera at the Staatliches Museum für Naturkunde Karlsruhe, Germany
Fossil and life restoration of Moravocoleus permianus (Tshekardocoleidae) from the Early Permian of the Czech Republic, representative of the morphology of early beetles
Beetle genera were mainly saprophages (detritivores) in the Permian and Triassic. During the Jurassic, herbivorous and then carnivorous genera became more common. In the Cenozoic, genera at all three trophic levels became far more numerous.
Fossil buprestid beetle from the Eocene (50 mya) Messel pit, which retains its structural color
Beetle body structure, using cockchafer.
A: head, B: thorax, C: abdomen.
1: antenna, 2: compound eye, 3: femur, 4: elytron (wing cover), 5: tibia, 6: tarsus, 7: claws, 8: mouthparts, 9: prothorax, 10: mesothorax, 11: metathorax, 12: abdominal sternites, 13: pygidium.
Front view of the head of Lamia textor
Polyphylla fullo has distinctive fan-like antennae, one of several distinct forms for the appendages among beetles.
Acilius sulcatus, a diving beetle with hind legs adapted as swimming limbs
Checkered beetle Trichodes alvearius taking off, showing the hard elytra (forewings adapted as wing-cases) held stiffly away from the flight wings
A beetle's body systems
Punctate flower chafers (Neorrhina punctata, Scarabaeidae) mating
The life cycle of the stag beetle includes three instars.
Scarabaeiform larva of Hercules beetle
The ivory-marked beetle, Eburia quadrigeminata, may live up to 40 years inside the hardwoods on which the larva feeds.
Photinus pyralis, firefly, in flight
A dung beetle rolling dung
Hycleus sp. (Meloidae) feeding on the petals of Ipomoea carnea
A camouflaged longhorn beetle, Ecyrus dasycerus
Clytus arietis (Cerambycidae), a Batesian mimic of wasps
Blister beetles such as Hycleus have brilliant aposematic coloration, warning of their toxicity.
An Israeli Copper Flower-Chafer (Protaetia cuprea ignicollis) on a crown daisy (Glebionis coronaria)
1: Adult ambrosia beetle burrows into wood and lays eggs, carrying fungal spores in its mycangia. 
2: Larva feeds on fungus, which digests wood, removing toxins, to mutual benefit. 
3: Larva pupates.
Tenebrionid beetle in the Thar Desert
The fogstand beetle of the Namib Desert, Stenocara gracilipes, is able to survive by collecting water from fog on its back.
A scarab in the Valley of the Kings
Cotton boll weevil
Larvae of the Colorado potato beetle, Leptinotarsa decemlineata, a serious crop pest
Coccinella septempunctata, a predatory beetle beneficial to agriculture
Mealworms in a bowl for human consumption
Zopheridae in jewellery at the Texas A&M University Insect Collection
"Remarkable Beetles Found at Simunjon, Borneo". A few of the 2,000 species of beetle collected by Alfred Russel Wallace in Borneo
Titan beetle, Titanus giganteus, a tropical longhorn, is one of the largest and heaviest insects in the world.
Scydosella musawasensis, the smallest known beetle: scale bar (right) is 50 μm.
Hercules beetle, Dynastes hercules ecuatorianus, the longest of all beetles
iridescent Protaetia cuprea feeding on thistle
iridescent Protaetia cuprea feeding on thistle

Beetles are insects that form the order Coleoptera, in the superorder Endopterygota.

In these insects, the testes are tubular and the first abdominal sternum (a plate of the exoskeleton) is divided by the hind coxae (the basal joints of the beetle's legs).


An Anthomyiidae species showing characteristic dipteran features: large eyes, small antennae, sucking mouthparts, single pair of flying wings, hindwings reduced to clublike halteres
Fossil brachyceran in Baltic amber. Lower Eocene, c. 50 million years ago
Fossil nematoceran in Dominican amber. Sandfly, Lutzomyia adiketis (Psychodidae), Early Miocene, c. 20 million years ago
Gauromydas heros is the largest fly in the world.
Head of a horse-fly showing large compound eyes and stout piercing mouthparts
A head of a fly, showing the two compound eyes and three simple eyes clearly.
A cranefly, showing the hind wings reduced to drumstick-shaped halteres
Tabanid fly in flight
Mating anthomyiid flies
Life cycle of stable fly Stomoxys calcitrans, showing eggs, 3 larval instars, pupa, and adult
A calliphorid "bubbling"
The large bee-fly, Bombylius major, is a Batesian mimic of bees.
Petrus Christus's 1446 painting Portrait of a Carthusian has a musca depicta (painted fly) on a trompe-l'œil frame.
An Anopheles stephensi mosquito drinking human blood. The species carries malaria.
Diptera in research: Drosophila melanogaster fruit fly larvae being bred in tubes in a genetics laboratory
Casu marzu is a traditional Sardinian sheep milk cheese that contains larvae of the cheese fly, Piophila casei.

Flies are insects of the order Diptera, the name being derived from the Greek δι- di- "two", and πτερόν pteron "wing".

Each of the fly's six legs has a typical insect structure of coxa, trochanter, femur, tibia and tarsus, with the tarsus in most instances being subdivided into five tarsomeres.


Drawings of Embia major winged male, male nymph and adult female "from the Himalayas" by Augustus Daniel Imms, 1913
The male's wings are stiffened and inflated as hemolymph fills sinus veins for flight; a crosswise crease allows them to fold in half to prevent damage when the insect runs backwards in a gallery.
Adult female in gallery
Web on a stone wall
Egg on gallery wall
First instar larva in gallery

The order Embioptera, commonly known as webspinners or footspinners, are a small group of mostly tropical and subtropical insects, classified under the subclass Pterygota.

It is these silk glands on the front tarsi that distinguish the embiopterans; other noteworthy characteristics of this group include three-jointed tarsi, simple wing venation with few cross veins, prognathous (head with forward-facing mouthparts), and absence of ocelli (simple eyes).


Approximate relative diversity of extant millipede orders, ranging from ca. 3,500 species of Polydesmida to 2 species of Siphoniulida
Octoglena sierra (Colobognatha, Polyzoniida)
Anadenobolus monilicornis (Juliformia, Spirobolida)
Harpaphe haydeniana (Polydesmida)
Pauropods are thought to be the closest relative of millipedes.
A representative millipede and centipede (not necessarily to scale)
Representative body types of the Penicillata (top), Pentazonia (middle), and Helminthomorpha (bottom)
Anterior anatomy of a generalized helminthomorph millipede
Paranota of polydesmidan (left) and platydesmidan millipedes
A female Illacme plenipes with 618 legs (309 pairs)
Epibolus pulchripes mating; the male is on the right
Growth stages of Nemasoma (Nemasomatidae), which reaches reproductive maturity in stage V
A Sceliages beetle transporting a millipede carcass
Ammodesmus nimba from Guinea, West Africa, curled in a defensive coil
Psammodesmus bryophorus camouflaged with symbiotic mosses
Giant fire millipede (Aphistogoniulus corallipes), Madagascar
Spotted snake millipedes can be agricultural pests.
Flat millipede found in the Mount Cameroon Forest

Millipedes are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments; they are known scientifically as the class Diplopoda, the name derived from this feature.

Millipedes are preyed on by a wide range of animals, including various reptiles, amphibians, birds, mammals, and insects.


Scorpions are predatory arachnids of the order Scorpiones.

Scorpions are predatory arachnids of the order Scorpiones.

Allopalaeophonus, formerly called Palaeophonus hunteri, from the Silurian of Scotland
Palaeophonus nuncius, a Silurian fossil from Sweden
Centruroides vittatus, the striped bark scorpion, a member of Buthidae, the largest family of scorpions
Heterometrus laoticus, the Vietnam forest scorpion, a member of the family Scorpionidae
Scorpion anatomy (dorsal view of Cheloctonus jonesii):
1 = Cephalothorax or Prosoma;
2 = Preabdomen or Mesosoma;
3 = Tail or Metasoma;
4 = Claws or Pedipalps;
5 = Legs;
6 = Mouth parts or Chelicerae;
7 = Pincers or Chelae;
8 = Moveable claw or Tarsus;
9 = Fixed claw or Manus;
10 = Stinger or Aculeus;
11 = Telson (anus in previous joint);
12 = Opening of book lungs
Ventral view: the pectines have a comblike structure in an inverted V shape.
Stinger of an Arizona bark scorpion
Centruroides limpidus in its rocky shelter
A few scorpions squirt venom to deter predators.
Scorpion feeding on a solifugid
Male and female scorpion during promenade à deux
Compsobuthus werneri female with young
Arizona bark scorpion, one of the few species whose venom is deadly to humans
The deathstalker's powerful venom contains the 36-amino acid peptide chlorotoxin (ribbon diagram shown). This blocks small-conductance chloride channels, immobilizing its prey.
Scorpion pose in yoga has one or both legs pointing forward over the head, like a scorpion's tail.
Late period bronze figure of Isis-Serket
"Scorpion and snake fighting", Anglo-Saxon Herbal, c. 1050
The constellation Scorpius, depicted in Urania's Mirror as "Scorpio", London, c. 1825
A scorpion motif (two types shown) was often woven into Turkish kilim flatweave carpets, for protection from their sting.

Scorpions primarily prey on insects and other invertebrates, but some species hunt vertebrates.

The cephalothorax comprises the carapace, eyes, chelicerae (mouth parts), pedipalps (which have chelae, commonly called claws or pincers) and four pairs of walking legs.


Fly of the suborder Cyclorrhapha.

Fly of the suborder Cyclorrhapha.

Head of a female housefly with two large compound eyes and three ocelli
Housefly mouthparts, showing the pseudotracheae, semitubular grooves (dark parallel bands) used for sucking up liquid food
A housefly wing under 250x magnification
Micrograph of the tarsus of the leg showing claws and bristles, including the central one between the two pulvilli known as the empodium
Houseflies mating
Housefly larva and adult, by Amedeo John Engel Terzi (1872–1956)
Housefly pupae killed by parasitoid wasp larvae: Each pupa has one hole through which a single adult wasp has emerged; the wasp larvae fed on the housefly larvae.
Housefly killed by the pathogenic fungus Entomophthora muscae
Housefly lapping up food from a plate
Philadelphia Department of Health poster warning the public of housefly hazards (c. 1942)
Detail of a 1742 painting by Frans van der Mijn that uses a housefly in a Renaissance allegory of touch theme
William Blake's illustration of "The Fly" in Songs of Innocence and of Experience (1794)

Houseflies have chemoreceptors, organs of taste, on the tarsi of their legs, so they can identify foods such as sugars by walking over them.

The housefly is, however, thought to exhibit multiple mechanisms for sex determination, such as male heterogamy (like most insects and mammals), female heterogamy (like birds), and maternal control over offspring sex.


Green mantis in a backyard in Sydney, 2020
Head of Archimantis latistyla, showing the compound eyes and labrum
Tenodera sinensis feeding on a cricket
Aggressive mimicry: Malaysian orchid mantises are camouflaged pink or yellow, matching the coloration of local orchids.
Sexual cannibalism in Mantis religiosa
Bronze ink brush rest in the shape of a mantis, Edo period, Japan, c. 1800
In Island, Aldous Huxley reflected on death as a pair of Gongylus gongylodes mated.
Grandmasters of the Shaolin Temple, Shi DeRu and Shi DeYang, demonstrating the Southern Praying Mantis style of martial art
Gray adult female Carolina mantis in human hand
Leaf mimicry: Choeradodis has leaf-like forewings and a widened green thorax.
Adult female Iris oratoria performs a bluffing threat display, rearing back with the forelegs and wings spread and mouth opened.
The jeweled flower mantis, Creobroter gemmatus: the brightly colored wings are opened suddenly in a deimatic display to startle predators.
Some mantis nymphs mimic ants to avoid predators.
Mantis religiosa mating (brown male, green female)
Stagmomantis carolina laying ootheca
Recently laid M. religiosa ootheca
Hatching from the ootheca
Sphodromantis lineola molting

Mantises are an order (Mantodea) of insects that contains over 2,400 species in about 460 genera in 33 families.

Their similarity is an example of convergent evolution; mantidflies do not have tegmina (leathery forewings) like mantises, their antennae are shorter and less thread-like, and the raptorial tibia is more muscular than that of a similar-sized mantis and bends back farther in preparation for shooting out to grasp prey.